Recycling your bits of broken crayon into new crayons is always a fun activity. Have you ever built a solar oven to recycle your crayons in?
When the sun is hot and you're looking for something to do with your kids or students, this makes for an engaging STEAM project. Not only will you create something new that you can make art with, there are science and engineering concepts inherent in each step of the process. Plus, making crayons in the solar oven is adaptable across a wide range of ages.
Create an engineering challenge out of designing a solar oven, or build a simple one and focus on the science of heat transfer, phase changes and melting point. If the kids are really young it is a great opportunity to identify and sort colors.
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Build a Solar Oven
First, decide how you will go about building your solar oven. You can make this an engineering challenge in and of itself. I had kids build them annually for years and it is always a super engaging learning experience. You can see how I've given students a solar oven engineering design challenge here.
While I enjoy seeing kids create their own solar oven designs, this time around we were focused on the recycled crayon portion of this project. So we built a solar oven out of a pizza box with these directions from Science Buddies.
Preparing the Crayons for Recycling
First you'll need to gather up the bits and bobs of crayons from the crayon box. This crayon prep work is excellent for small hands.
We measured to determine which crayons were keepers and which would be recycled. Then we made sure all the crayons that we were using to recycle had been peeled.
Next we sorted the crayon bits by color. There is a lot of discussion surrounding this. Do they have to be the same shade of the color? Can you make a rainbow crayon? The sky is the limit here, so anything goes.
Then we put the sorted crayons into our silicone mold. You can use any shape silicone mold, or even a muffin tin. If you choose to use a muffin tin, spray with cooking spray ahead of time to assure your new crayons slip right out.
We like this set of molds that looks like building bricks and LEGO mini-figures. We got ours on Amazon, but you can find silicone molds in a variety of shapes anywhere they sell candy making and baking supplies.
As you can see the silicone molds are a bit stained. They have been used to make milk plastic (the directions for milk plastic can be found in the STEAM Kids activity book, which you can find digitally here or in print here) and many times for recycled crayons. The silicone molds work great for this, but I would suggest dedicating a set specifically for craft projects and science experiments and not for food.
Make Recycled Crayons with Solar Power
Find a spot that will remain sunny for several hours. Take note of the direction and angle of the sun and set up the oven where the sun is shining down. You may need to adjust the position of your oven throughout the day as the sun shifts. You can even build a sundial while you wait for your crayons to melt!
How long does it take before your crayons begin to melt? You may want to put a thermometer inside your oven, or use an infrared surface thermometer and periodically check the temperature.
Once the crayon bits have turned completely into a puddle, then very carefully move the solar oven into the shade, or bring it inside where it is cooler. We brought ours inside in the late afternoon. Just to be sure we didn't break any bits that hadn't solidified all the way we waited until the following morning to pull them out of the mold.
Once they are completely cooled, carefully pull them out of the mold.
Science Lessons with the Solar Oven
There are so many learning opportunities within this project. You could think about melting point and phase changes. With older children this may lead to further study. Check out this middle school lesson about melting point from the American Chemical Society. Or try this melting point experiment I like to do around Thanksgiving with pop-up poultry timers.
With younger children a discussion about melting point and phase change could include a simple experiment to see what materials melt in the heat of our hand. Does our hand make as much heat as the Sun? Does a crayon melt in our hand? How about a chocolate chip? Different materials have different properties.
We also took the opportunity to discuss why the construction paper had changed color after being exposed to the sun for hours. If this is something you observe, you could continue this study by making nature prints with construction paper and natural objects in the sun. Or you could extend this idea to help answer the question, "Why do we need sunscreen?" and experiment with sunscreen and construction paper.
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